spparms('key',value)
spparms
values = spparms
[keys,values] = spparms
spparms(values)
value = spparms('key')
spparms('default')
spparms('tight')
spparms('key',value)
sets one or more of the tunable parameters used in the sparse linear equation operators, \
and /
, and the minimum degree orderings, colmmd
and symmmd
.
The meanings of the key
parameters are
--------------------------------------------------------------------------- 'spumoni' Sparse Monitor flag. 0 produces no diagnostic output, the default. 1 produces information about choice of algorithm based on matrix structure, and about storage alloca tion. 2 also produces very detailed information about the minimum degree algorithms. 'thr_rel', 'thr_abs' Minimum degree threshold isthr_rel*mindegree+thr_abs
'exact_d' Nonzero to use exact degrees in minimum degree. Zero to use approximate degrees. 'supernd' If positive, minimum degree amalgamates the super nodes everysupernd
stages. 'rreduce' If positive, minimum degree does row reduction everyrreduce
stages. 'wh_frac' Rows withdensity > wh_frac
are ignored incolmmd
. 'autommd' Nonzero to use minimum degree orderings with \ and/
. 'aug_rel', Residual scaling parameter for augmented equations 'aug_abs' isaug_rel
*max(max(abs(A))) + aug_abs
For example,aug_rel = 0
,aug_abs = 1
puts an un scaled identity matrix in the (1,1) block of the aug mented matrix. ---------------------------------------------------------------------------
spparms
, by itself, prints a description of the current settings.
values = spparms
returns a vector whose components give the current settings.
[keys,values] = spparms
returns that vector, and also returns a character matrix whose rows are the keywords for the parameters.
spparms(values)
, with no output argument, sets all the parameters to the values specified by the argument vector.
value = spparms('key')
returns the current setting of one parameter.
spparms('default')
sets all the parameters to their default settings.
spparms('tight')
sets the minimum degree ordering parameters to their tight settings, which can lead to orderings with less fill-in, but which make the ordering functions themselves use more execution time.
The key parameters with the default
and tight
values are
------------------------------------------------------------------- Keyword
Default
Tight
------------------------------------------------------------------- values(1) 'spumoni' 0.0
values(2) 'thr_rel' 1.1
1.0
values(3) 'thr_abs' 1.0
0.0
values(4) 'exact_d' 0.0
1.0
values(5) 'supernd' 3.0
1.0
values(6) 'rreduce' 3.0
1.0
values(7) 'wh_frac' 0.5
0.5
values(8) 'autommd' 1.0
values(9) 'aug_rel' 0.001
values(10) 'aug_abs' 0.0
-------------------------------------------------------------------
\
,colmmd
,spaugment
,symmmd
(c) Copyright 1994 by The MathWorks, Inc.